1. Field of the Invention
This invention relates to the field of information networks, and more particularly relates to a protocol for configuring routes over a network.
2. Description of the Related Art
Today""s networks carry vast amounts of information. High bandwidth applications supported by these networks include streaming video, streaming audio, and large aggregations of voice traffic. In the future, these bandwidth demands are certain to increase. To meet such demands, an increasingly popular alternative is the use of lightwave communications carried over fiber-optic cables. The use of lightwave communications provides several benefits, including high bandwidth, ease of installation, and capacity for future growth.
Optical infrastructures are capable of transmission speeds in the gigabit range, which helps address the ever-increasing need for bandwidth mentioned above. Such infrastructures employ various topologies, including ring and mesh topologies. In order to provide fault protection, ring topologies normally reserve a large portion (e.g. 50% or more) of the network""s available bandwidth for use in restoring failed circuits. However, ring topologies are capable of quickly restoring failed circuits. This capability is important in providing reliable service to customers, and is particularly important in telephony applications, where a failure can result in alarms, dropped calls, and, ultimately, customer dissatisfaction and lost revenue. In a similar vein, because of bandwidth demands, protocol overhead related to provisioning, restoration, and other functions should be kept to a minimum in order to make the maximum amount of bandwidth available for use by customers.
An alternative to the ring topology, the mesh topology reduces the amount of bandwidth needed for protection. The mesh topology is a point-to-point topology, with each node in the network connected to one or more other nodes. Because a circuit may be routed through various combinations of the network""s nodes and over the various links which connect them, excess capacity through a given node or over a given link can serve to protect several circuits. However, the restoration of a circuit following a failure in a mesh topology can consume a relatively large amount of time.
In one embodiment, the present invention reduces the time and resources required to restore a failed circuit (or provision a new circuit) in an optical network by partitioning the nodes of an optical network into zones. The time and resources required are reduced, for example, by localizing the required actions to the zone in which the failure occurred. Localization is effected through the use of a node that acts as a substitute for the source or destination node, as the case may be. This substitute node is referred to herein as a proxy node. The proxy node will normally be a boundary node for the zone in which no failure occurred. If a failure occurs between zones, both boundary nodes can act as proxies for their respective non-boundary nodes, or a full restoration may instead be performed.
According to one embodiment of the present invention, a method is provided for operating a network. The method, in one embodiment, begins by grouping a plurality of nodes into zones, where the network includes the plurality of nodes. At least one of the nodes in each one of the zones is one of a plurality of boundary nodes, and each of the boundary nodes in each one of the zones is coupled to a boundary node in another of the zones by one of a first number of inter-zone optical links. One of the zones includes a number of nodes, each of which is coupled to at least one other of the nodes by one of a second number of intra-zone optical links. Next, a non-boundary node is configured to transmit network information to other of the nodes. The non-boundary node is a node in the zone that is not a boundary node. Finally, a boundary node in the zone is configured to limit transmission of the network information through itself to other of the boundary nodes. The network information so limited can be restoration information (in the event of a failure), network topology information, and/or other network information.
According to another embodiment of the present invention, a network includes a plurality of nodes, a plurality of inter-zone optical links, and a plurality of intra-zone optical links. The nodes are grouped into zones, and each one of the zones includes at least a first number of the nodes, at least one of which is a boundary node. A boundary node in each one of the zones is coupled to a boundary node in at least one of the other zones by at least one of the inter-zone optical links One of the zones includes a second number of nodes, which including a first boundary node and a first non-boundary node. The first non-boundary node is one of the second number of the nodes that is not the first boundary node, and each one of the second number of nodes is coupled to at least one other of those nodes by at least one of the intra-zone optical links. The non-boundary node is configured to transmit network information to other of the nodes, while the first boundary node is configured to limit transmission of network information through itself to at least one other of the boundary nodes.
The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below.